Method and device for handling telephone calls directed to non-reachable mobile phones

ABSTRACT

A method for handling telephone calls directed to a non-reachable mobile phone, and for handling data pertaining to them, wherein:  
     I—provided the call diversion service to a different number, or the answering service, have not been enabled, the phone call is routed towards a phone call data management and storage device, when the mobile phone called user is non-reachable, out to the fact that is in the detach mode or is temporarily out of the range reachable by radio-frequency signals; II—at the time mobile phone is again reachable, a notification is transmitted to the subscriber number of the telephone call; the notification being effected in the form of SMS, which contain phone call data of missed phone calls performed during the period while the mobile phone was not reachable.

FIELD OF THE INVENTION

[0001] The present invention generally refers to the problem ofestablishing a communication with a subscriber in a cellular radiomobile network, and more particularly it relates to a telecommunicationservice through a cellular radio mobile network, which allows asubscriber to acquire the telephone number of the subscriber who triedto call him while he was not reachable due to radio signalling absence,or because the mobile phone was in the detach mode. The invention isconcerned both with the method for implementing this service and withthe functions of special devices employed when providing the same.

BACKGROUND ART

[0002] Recent estimates suggest that for every telephone network dealer,who at present is concerned with the public radio mobile service inItaly, there are daily tens of a million telephone calls which areunsuccessful because the “target” mobile phone is not reachable or is inthe detach mode.

[0003] In other words, notwithstanding the increased use of telephoneanswering systems (answering services), and call diversion services, itnevertheless happens, that in some special conditions, more than 400calls/second are missed, thereby limiting the extent of outgoing trafficor, in any case, providing a restricted or Partially complete service tosubscribers.

[0004] The basic difficulty found by a network administrtor whentackling this kind of problem, is that of getting through a considerabletraffic.

[0005] In fact, the problem of the recording and management—at the sametime—of such a noticeable amount of data due to the high number ofunsuccessful calls, the difficulties caused by a consistent evaluationof the geographical load of this service, the management of possiblenetwork failures, etc., have led to the situation that—up to now—asolution to this problem has neither been considered nor put intopractice. This problem does not lend itself to a simple solution, sincemany reasons may be the cause for the impossibility of establishing acommunication:

[0006] the radio mobile phone may be in the detach mode, the networkhaving acquired the signal which confirms this fact (detach);

[0007] the battery is discharged or is disconnected from its operativeposition, or the SIM card is off;

[0008] a condition may exist wherein the transceiver station is notreachable or not visible, as the radio channel is notoriously veryaleatory; etc.

[0009] At last, it would be necessary—in any case—to verify the possibleenabling of the call diversion service to the answering system or to afurther telephone number. On the other hand, these conditions accordingto which it is impossible to reach a called subscriber, have till nowbeen accepted by the users of the radio mobile service as intrinsicallyforeseeable but totally inevitable. In other words, this problemrelating to the impossibility of establishing a connection has neverbeen posed, because in comparison with the fixed network it was evidentthat the cellular telephone network would necessarily lead to thisdrawback, due to the intrinsic nature of the principle of operation of amobile phone, which could momentarily be non reachable or in the detachmode.

[0010] An object of the present invention is to provide handlingprocedures for managing telephone calls directed to a radio mobilephone, which allow to improve the service, by eliminating the drawbacksdue to communication barriers caused by the problem of a “non-reachablemobile phone”.

[0011] A further object of the present invention is to increase thenumber of free basic services offered to the users by the networkdealer.

[0012] A last object of the present invention is to provide a method forhandling calls to a non-reachable radio mobile phone, and for handlingthe related, acquired information, the method employing standardprotocols, technologies and components in the field of cellular radiomobile phones, in order to permit easy maintenance and reduce the costof the method implementation

DISCLOSURE OF INVENTION

[0013] These and further objects which will be apparent from thedescription, are obtained through a method for handling telephone callsdirected to a non-reachable radio mobile phone and for handlinginformation associated to the calling subscriber (like telephone number,time of the telephone call, and any additional information), wherein themethod is started (triggered) by an event such as a vocal call, which inturn originates a notification through a recordable SMS text channel,and comprises the two distinct basic steps of:

[0014] I) routing the telephone call to a device for storage andmanagement of data (information) relating to the phone call, when thecalled subscriber is not reachable, due to the subscriber mobile phonebeing in the detach mode or due to the absence of a radio-frequencysignal, and when, at the same time, the call diversion service towardsthe answering service or another phone number is not operative;

[0015] II) transmitting, that is notifying, to the called subscriber, atthe moment the mobile phone is reachable again, all SMS texts includingdata relating to the calls missed in the period when the subscriber wasnot reachable; the method being based on a protocol, in which the usualsteps sequence for performing a mobile telephone network call, is firststarted and thereafter immediately interrupted after the signaling andacquisition of the subscriber identification, and this steps sequence isresumed at the time it has been ascertained that the cellular radiomobile phone is reachable again, but actuating this time an SMS textchannel, so as to completely eliminate the actual serial operative stepsequence (transaction) typical of a voice communication protocol,thereby producing, in fact, a traffic having a virtual nature.

[0016] The method disclosed herein is basically different from the knowntelephone call diversion to the answering service, which involves in anycase a complete serial operative calling and answering step sequence(transaction) and therefore a cost for the user, which depends from thetime period during which the channel is engaged. The service has beenrealized using TACS, GSM, or GPRS technology, and it could also berealized by employing UMTS technology.

[0017] As far as the user is concerned, this service works according tothe following steps:

[0018] If a user is called while he is not reachable (cellular mobilephone in detached mode, or absence of radio-frequency signal), thecalling user receives a vocal message informing him about the fact thatthe called user cannot be reached (this service is automatic, withoutany sort of control option being performed by the calling user).

[0019] Immediately after the called user is reachable again, he receivesan SMS notification, including an indication of all telephone callsmissed during the period while he was not reachable. The notification issent by means of an SMS text to the owners of a GSM radio mobile phone,and to the owners of TACS radio mobile phones adapted to receive andtransmit SMS text messages, whereas the notification is sent in the formof vocal SMS in case of TACS users whose cellular radio mobile phone isnot adapted to handle SMS text. The phone number of the callingsubscriber, the time of the telephone call, and any other relevantinformation relating to the calling subscriber and/or the calledsubscriber are transmitted at the same time. In case a user (with thesame phone number) has called several times, only an indicationpertaining to the most recent phone call will be provided. Moreover, ifthe number of missed telephone calls exceeds the available space in asingle SMS, further SMS will be sent The information concerning missedtelephone calls may be stored only for a maximum predetermined timeperiod.

[0020] The service is not actuated in the following circumstances:

[0021] The call diversion service is already active, towards ananswering system or towards a different phone number,

[0022] The phone number of the calling user is not available or is notpresented (e.g. a phone call from abroad, or in case of a hidden number,etc.)

[0023] The called user is roaming abroad

BRIEF DESCRIPTION OF DRAWINGS

[0024] Preferred embodiments of the invention are described in thefollowing for illustrative purposes only, without limiting thegenerality and possible applications thereof said embodiments beingshown in the annexed figures, in which:

[0025]FIG. 1 is a schematic view of a network architecture, providing anindication of the method of operation of the present invention;

[0026]FIG. 2 is a block diagram of a fundamental procedure in the ambitof the method according to the present invention;

[0027]FIG. 3 is a block diagram illustrating a further essentialprocedure relating to the method of the present invention

BEST MODES OF CARRYING OUT THE INVENTION

[0028] It is now useful, before starting with the detailed description,to preliminarily introduce a list of symbologies and abbreviationsactually in use in the technical field to which the invention refers.

[0029] 1. DETACH: the user has turned off his radio mobile cellularphone by pushing the “OFF” key.

[0030] 2. HLR Home Location Register: Database containing data relatingto registered cellular phones.

[0031] 3. IMSI: radio mobile identity of the SIM card.

[0032] 4. IP: network address defined in the Internet protocol.

[0033] 5. IAM Initial Address Message: Signaling message containinginformation relating to the calling/called person

[0034] 6. ISUP ISDN User Part: GSM network signaling

[0035] 7. MAP Mobil Application Part: it denotes (when MAP GSM isimplied) the protocol used by the nodes of the GSM network to manage theusers mobility.

[0036] 8. MSC mobile switching center: switching center for mobiletelephony

[0037] 9. MSISDN Mobil Station Integrated Service Digital Network: itdenotes the number of the mobile phone (e.g. 0338 451845)

[0038] 10. PAGING: a radio signal diffused from the MSC/VLR to informthe radio mobile phone that a call has arrived

[0039] 11. PLMN: Public Land Mobile Network

[0040] 12. PSTN: Public Switch Telephone Network

[0041] 13. ROAMING: denotes a condition wherein a GSM mobile phonehappens to be connected to a network which differs from the networkwhich issued the GSM card of the mobile phone.

[0042] 14. SMS-C: service center for short messages

[0043] 15. STP Signaling Transfer Protocol: it denotes a function of thesignaling telephone network, which allows to transfer a signalingmessage to its destination, passing through intermediate nodes.

[0044] 16. TGDS TACS/GSM Gateway Delivery System: MultifunctionalHardware and Software Platform, implemented for integration of wirelessmessage systems operative procedures.

[0045] 17. UCP Universal Computer Protocol: Protocol used in the datatransmission towards the service center SMS-C

[0046] 18. VLR Visitor Location Register: database containinginformation relating to the actual position of the mobile phone.

[0047] Referring now to FIG. 1, this figure schematically shows thearchitecture used for providing this service, with dotted linesindicating the functions of standard protocol stacks; on the other hand,FIGS. 2 and 3 denote the respective operative method used to carry outthis service, which includes the following steps:

[0048] I) the calling subscriber 1′, 1″ dials (step 30) the destinationor “target” number and performs his telephone call by interconnectinghimself to a PSIN telephone network 4, in case the phone call iseffected from a fixed line 1′, or to the telephone network PLMN 5, incase the phone call is effected from a mobile phone 1″,

[0049] II) the original switching center MSC 2 interrogates thesubscribers register 3 (hereafter HLR), at 31, by means of the STP 10,by asking the roaming destination number,

[0050] III) the HLR 3 checks at 32 (based on the VLR number), if themobile phone is roaming abroad (this step is valid only for the GSMnetwork).

[0051] if the answer is “YES”, the phone call is handled according tothe usual procedure 33 provided for in GSM networks,

[0052] if the answer is “NO” the procedure continues through the stepsdescribed below,

[0053] IV) the HLR 3 checks if the destination mobile phone is in theDETACH mode (34):

[0054] IV i) if the answer is “NO”, it transmits (35) to the originalswitching center MSC 2, the roaming number of the center MSC/VLR inwhich the destination number is registered (destination center) and themethod continues as described below in steps V and subsequent ones,which relate to checking if the mobile phone is reachable;

[0055] IV ii) if the answer is “YES”, it is checked—at 36—if thedestination number has enabled the call diversion service towards itsown answering service or towards another phone number:

[0056] if the answer is “YES”, the number towards which the calldiversion is active is returned (at 37) to the original exchange 2(MSC), and the method proceeds by going back to step II;

[0057] if the answer is “NO”, the number of the device 9 for the storageand management of phone calls (hereafter also called “pagingmanagement”) is returned (at 38) to the original exchange (MSC) 2, andthen the method proceeds as described in step VI.

[0058] V In case the preliminary check on the DETACH mode of the mobilephone has led to a negative result, the destination center performs afurther test 40 in order to establish if the destination (“target”)mobile phone is reachable:

[0059] if the answer is “YES”, the usual procedure for a phone call isstarted at 33, following the common procedure provided for in radiomobile phone systems.

[0060] if, on the other hand, the mobile phone is not reachable, aconnection is established at 38, towards the number of the device 9 forthe paging management, and the method proceeds according to thefollowing step.

[0061] VI) If the mobile phone is turned off or is not reachable, and nocall diversion is enabled, the calling user receives an announcement andthe phone call is routed towards the device 9 for the paging management.

[0062] In order to increase the degree of reliability the design isrealized in such a way as to use two nodes of paging management Bothnodes share the same Data Base 14 of the phone calls, which isduplicated in the respective sites. In order to manage correctsynchronization and management of the two Data Base systems, and inorder to avoid access conflicts on the same records (as would occur whentwo users call at the same time the same person whose mobile phone isturned off or not reachable by a radio-frequency signal), it was decidedto define two series of different numbering on the HLR 3 forcall-forwarding to the paging management device (these series are called“Call Forward Number MSISDN Paging_(—)1” and “Call Forward Number MSISDNPaging_(—)2”). The total number of numberings will be 10 (in order toleave a margin for possible future introductions of other pagingmanagement platforms), and they are formed by adding at the end of thenumbering “47000”, the last number of the MSISDN of the called user withrespect to whom the service is made active.

[0063] To this purpose, the paging management device 9,—that is thedevice for the storage and management of information relating to phonecalls towards a non-reachable mobile phone—, satisfies a plurality ofspecific functional requirements which relate to the ability ofcooperating, through the management of the protocol ISUP, with theswitching nodes of the GSM network, and to the ability of extracting thecalling number from the ISUP IAM message for the phone calls directed toa non-reachable mobile phone or in case of absence of a radio-frequencysignal; furthermore there is provided the possibility of storing in adedicated Data Base 14, all information related to phone calls directedto each mobile phone not reachable due to absence of radio frequencysignal.

[0064] Moreover, the paging management device 9 is suited to cooperatewith the HLR, through the management of the MAP protocol, for aswitching request with regard to the return of momentarily non reachablemobile phones, inside the area reachable by radio-frequency signals. Atlast, it is also capable of interfacing itself,—through the managementof the UCP protocol—, with the SMS service center 11 of the GSMswitching center, in order to send text messages towards the mobilephones which have returned inside the area where radio-frequency signalsare active.

[0065] On the other hand, under the aspect of the procedural realizationof specific functions according to the present invention, the pagingmanagement device 9 successively performs the following operations:

[0066] I—It receives, at 50, only the signaling component of the phonecall, it extracts the number of the calling subscriber from the IAMmessage of the ISUP signaling, it records the hour/date of the telephonecall (with an accuracy of one second), and then it emits an appropriatedeliver message (at 51) with respect to the MSC/VRL which is sending thedata This allows the MSC/VLR to possibly send a courtesy message (at52), to the calling user, to deliver the phone call so as to release thephonic channel;

[0067] II—it activates a check at 53, in order to determine whether thecalling number is already in the list of numbers that already tried toreach this particular subscriber, depending on the result of this check,it performs the following operations:

[0068] provided this number is already in the list of calling numbersfor that subscriber, it replaces (at 54) the hour/date of the last phonecall performed by this user number, with the hour/date recorded duringthe preceding step;

[0069] if, on the other hand, this number is not in the list of callingnumbers for that subscriber, it adds this number to the list (at 55),together with an indication of the hour/date of the last telephone call,

[0070] III—if from a test 56, it follows that the phone call correspondsto a first phone call, directed to the called subscriber during theperiod when he was not reachable, a request is made (at 57) to the HLR 3(through MAP SET MESSAGE WAITING DATA) to receive a notificationimmediately after the “target user”, that is the subscriber, is againreachable.

[0071] When the addressee of the telephone call is again reachable, theHLR 3 communicates this fact to the paging management device 9.According to a preferred embodiment of the present invention, once thenotification has been received, the paging management device subdividesthe number list associated to the target mobile phone, into groups offour elements each, and for each of said groups it defines a textmessage to be sent to the user, containing information related to thephone calls comprised in this group.

[0072] The paging management device sends to the short message servicecenter, 11, the above defined messages, through the UCP protocol,indicating as addressee the number of the destination (that is, target)mobile phone.

[0073] Finally, the SMS-C sends the messages to the destination mobilephone at the time it is reachable again.

[0074] The system that realizes the network architecture according tothe above description is suited to provide a very high capacity oftraffic management: it is able to manage 350 phone calls per second, andup to 10 millions phone calls per day.

[0075] These performances are obtained through a logical subdivision ofthe network load on a plurality of nodes and through the use oftechnologies, which are partly already known and already used in thefield of telephony, but which are combined by means of the necessaryimplementations, extensions and modifications, so as to be able tofinally provide the users with a new free service.

[0076] This service is already (default) enabled, although the user mayrequest its deactivation by calling and dialing a new special option ofa voice menu; subsequently, he can also request reactivation of thisservice, by performing similar actions.

1. A method for handling telephone calls to a non-reachable radio mobilephone, and for handling data pertaining to them, like the telephonenumber of the calling subscriber, the time of the telephone call, andany additional information relating to the calling subscriber,characterized in that it is started by an event like a voice call, whichin turn originates a notification through a recordable SMS text channel,the method comprising the two following distinct steps of: I—routing thetelephone call to a device for storage and management of data relatingto the phone call, when the called subscriber is not reachable, due tothe subscriber mobile phone being in the detach mode or due to theabsence of a radio-frequency signal, and when, at the same time, thecall diversion service towards the answering service or another phonenumber is not operative; II—transmitting, that is noticing, to thecalled subscriber, at the moment the mobile phone is reachable again,all SMS texts including data relating to the calls missed in the periodwhen the subscriber was not reachable; the method being based on aprotocol, in which the usual steps sequence for performing a mobiletelephone line call, is first started and thereafter immediatelyinterrupted after the signaling and acquisition of the subscriberidentification, and this steps sequence is resumed at the time it hasbeen ascertained that the radio mobile phone is reachable again, butactuating this time an SMS text channel, so as to completely eliminatethe actual serial operative step sequence (transaction), typical of avoice communication protocol, thereby producing, in fact, a traffichaving a virtual nature:
 2. A method for handling telephone callsdirected to a non-reachable radio mobile phone, and for handling datapertaining to them, according to claim 1, characterized in that saiddata are acquired according to the following method steps: A) thecalling subscriber (1′, 1″) dials (30) the destination or “target”number and performs his telephone call; B) the original switching centerMSC (2) interrogates the subscribers register HLR (3), asking theroaming destination number, C) the HLR (3) checks (34) if the addressedmobile phone is in the DETACH mode: C i) if the answer is “NO”, ittransmits (35) to the original switching center MSC (2), the roamingnumber of the center MSC/VLR in which the destination number relative tothe destination center is recorded, and the method continues asdescribed below in steps D and subsequent ones, C ii) if the answer is“YES”, it is checked (36) whether the destination number has actuatedthe call diversion service towards its own answering service or towardsanother phone number: a) if the answer is “YES”, the number towardswhich the call diversion is active, is returned (37) to the original MSCcenter (2), and the method proceeds by repeating the above step B; b) ifthe answer is “NO”, the number of the device (9) for the storage andmanagement of phone calls is returned (38) to the original center MSC(2), and the method proceeds to step E; D) in case the preliminary checkon the DETACH mode of the mobile phone has led to a negative result, thedestination center performs also a test (40) in order to establish ifthe destination mobile phone is reachable: i)—if the answer is “YES”, iteffects (41) a phone call to the destination number, following thecommon procedure provided for in radio mobile phone systems; ii)—if, onthe other hand, the mobile phone is not reachable, a connection isestablished (38) with the number of the device (9) for storage andmanagement of phone calls, and then the method proceeds according to thefollowing sequence of operative steps; E) if the destination mobilephone is in the detach mode or is not reachable, and no call diversionis active, then the calling user receives an announcement and the phonecall is routed towards the device (9) for storage and management ofphone calls.
 3. A method for handling telephone calls directed to anon-reachable radio mobile phone, and for handling data pertaining tothem, according to claims 1 and 2, characterized in that a preliminarycheck (32) is performed on the HLR (3), based on the VLR number, todetermine whether the destination mobile phone is roaming abroad in caseof a GSM mobile phone network, and in that: i) in the affirmative case,the phone call is managed following the usual procedure (33) providedfor in GSM networks; ii) otherwise, the procedure (34) for determiningthe DETACH mode is followed, and thereafter the other steps provided forby this method are performed.
 4. A method for handling telephone callsdirected to a non-reachable mobile phone, and for handling datapertaining to them, according to claims 1 and 2, characterized in thatit comprises the implementation, on the HLR (3) and on the transportnetwork, of procedures which are apt to automatically transit theprocessing load towards at least a system (9) performing the storage andmanagement of phone calls, trough a virtualization of the subscriberaddressee by means of a fictitious call diversion.
 5. A method forhandling telephone calls directed to a non-reachable mobile phone, andfor handling data pertaining to them, according to claims 1 and 4,characterized in that it uses two phone call management and storagenodes, which share the same phone call Data Base (14), duplicated in therelative sites, by defining on the HLR two series of distinct numberingsfor redirecting the phone calls towards the device (9) for the storageand management of phone calls.
 6. A method for handling telephone callsdirected to a non-reachable mobile phone, according to claim 4,characterized in that it makes use of ten storage and management nodes,which are apt to share the same Data Base (14) of the telephone calls,repeated on the relative sites, based on the definition on the HLR often sets of distinct numberings of redirection of the called subscriber,wherein, for all ten sets of numberings it is provided that each numberis formed by adding the last number of the MSISDN of the called user onwhich the service is made active, at the end of an initial, predefinedand fixed numbering.
 7. A method for handling telephone calls directedto a non-reachable mobile phone, and for handling data pertaining tothem, according to claim 1, characterized in that it makes use of adevice (9) for the storage and management of phone calls, whichaccomplishes the following steps, in this order I—acquisition of onlythe signaling component relating to the phone call; exaction of thenumber of the calling subscriber, from the signaling IAM message;recording of the hour/date of the phone call; and emission of anappropriate deliver message with respect to the MSC/VLR which is sendingthe data, so that the same MSC/VLR may send a courtesy message to thecalling subscriber, in order to obtain the interruption of the phonecall and the release of the phonic channel; —checking whether thecalling number is included in the list of the numbers which have alreadytried to communicate with that particular subscriber, and performing thefollowing steps, based on the result of this check: a) provided thisnumber is already in the list of calling numbers for that addressee, thereplacement of the hour/date of the last phone call performed by thissubscriber number, with the hour/date recorded during the precedingstep; b) if , on the other hand, this number is not in the list ofcalling numbers for that subscriber, the addition of this number at theend of the list, together with an indication of the hour/date of thelast telephone call; III—if the phone call corresponds to a first phonecall, directed to the subscriber during the period when he was notreachable, performing a request to the HLR to receive a notificationimmediately after the addressee is reachable again; IV—when thetelephone call subscriber is reachable again, notification of this fact,from the HLR to said device (9) for storage and management of telephonecalls; V—once the notification has been received, editing of the textmessage by the device (9) for storage and management of telephone calls,said text message being that which must be sent to the destinationmobile phone and containing the data related to the registered telephonecalls; VI—transmission to the short message service center (11) from thedevice for storage and management of telephone calls, of the previouslyedited messages, making use of the UCP protocol, by indicating thecalled mobile phone subscriber number as addressee; VII—transmission ofsaid short messages to the destination mobile phone, performed by theshort message service center at the time the destination mobile phone isagain reachable.
 8. A device for the storage and management of datarelating to phone calls directed to a mobile phone, when the latter isin the detach mode, or when a radio-frequency signal cannot reach saidmobile phone, characterized in that it comprises: means apt tocooperate, through the management of the ISUP protocol, with theswitching nodes of the GSM network, and suited to extract the callingnumber from the ISUP IAM message, for telephone calls directed to nonreachable mobile phones, or in absence of a radio-frequency signal;means for storing and handling data relating to telephone calls directedto every mobile phone which is not reachable by a radio-frequencysignal; means apt to cooperate with the HLR, through the management ofthe MAP protocol, for performing a request of notification of the returnof the mobile phones inside the area reachable by radio frequencysignals; means apt to cooperate with the SMS-C of the GSM switchingnetwork, through the management of the UCP protocol, in order to sendthe SMS text messages to those mobile phones which have returned insidethe area which is reachable by radio-frequency signals.
 9. A method forhandling telephone calls directed to a non-reachable mobile phone andfor handling data pertaining to them, in which use is made of the devicefor storage and management of data according to claim 8, characterizedin that it comprises the following operative steps: I—routing of phonecalls initially directed to a non-reachable mobile phone, towards saiddevice (9) for storage and management of phone calls, with no chargebeing paid by the subscriber, said routing being performed when no calldiversion is active and when the mobile phone is not abroad,II—extraction from the IAM signaling message, of the calling subscribernumber relating to said phone calls directed to said non-reachablemobile phone, said extraction being performed by the phone call storageand management device; III—notification of the return of temporarilynon-reachable mobile phones, inside the area reachable byradio-frequency signals, said notification being performed from the HLRto the phone call storage and management device; IV—transmission of oneor more SMS, containing data of missed phone calls, wherein thistransmission is performed by the phone call storage and managementdevice (9) to those mobile phones which are again reachable.